Sparking plug



May 15,1928. 1,669,487 N. M. MARTIN SPARKING PLUG Filed June 11, 1926 /3 $31k J 2 22A Nzz \525 l l 2 Ms 4 z Patented May 15, 1928..

' UNITED STATES PATENT OFFICE.

NORMAN MACDONALD MARTIN, OF ALFRISION, ENGLAND.

SPARRING PLUG.

Application filed June 11, 1926, Serial No. 115,338, and in Great Britain October 23, 1925.

This invention relates to spark plugs for internal combustion engines, and more particularly relates to spark plugs of the'type in which the central electrode passes tlirough the plug body so that it may be removed'without having to unscrew the plug body from the engine. Heretofore in spark plugs of this type it has been proposed to provide a metal sleeve passing axially through insulation supported in the body, said sleeve being adapted to receive the central electrode by threading the electrode into the sleeve, the central electrode being removable by unscrewing it from the said sleeve. The object of this invention is to provide a simplified and eiiicient construction of spark plug which will enable the central electrode to be readily removed and cleaned and the engine to be primed without having to remove the spark plug body and without having to unscrew the electrode.

According to my invention a spark plug comprises in combination with a cylindrical or polygonal body having the usual threaded lower end, an electrode adapted to receive the usual lead and passing completely through a metal sleeve so that it may be readily pulled out of the sleeve or pushed home therein to its operative position, said sleeve having an upper integral threaded portion extending above the insulation to receive a nut insulated from the said body but readily accessible above the said body, the electrode being frictionally gripped inside the said sleeve by threading said nut upon the sleeve, the arrangement being such that by merely unscrewing said nut from the sleeve the electrode can be withdrawn from the plug merely by pulling it from the sleeve.

In order that this invention may be clearly understood and readily carried into effect I have appended hereto a sheet of drawings illustrating an embodiment of same, wherein Fig. 1 is a side elevation of a spark plug constructed in accordance with my invention; and

Fig. 2 is a central vertical section through my improved plug.

Referring to the drawings, it will be observed that my improved spark plug comprises a hollow metal body 1 having as usual an externally threaded base portion 2 whereby it may be screwed into the cylinder wall of an engine. Secured in any suitable manner within the plug body 1 is a member 3 of insulation which may consist of a single piece of material or of a laminated structure as shown. Firmly secured in any suitable manner within a central opening pro-- vided therefor in the member 3 is a metallic sleeve at the outer end of which projects beyond the outer end of the member 3 and is externally threaded. Formed centrally through the sleeve 4 is an inwardly tapering opening adapted to receive an inwardly tapered portion of an electrode 5, which elec trode is provided with an annular enlargement 7. A nut composed of an outer body of insulation 12 and an inner internally threaded metallic portion 13 firmly embedded or otherwise secured within said body 12 is adapted to be threaded onto the sleeve 4' to retain the electrode within said sleeve, said portion 13 to this end being inclusive of a suitable shoulder for engagement with the annular enlargement 7 of the electrode whereby, when the nut is threaded onto the sleeve, this shoulder, acting against the enlargement 7, forces the electrode into rigid engagement with the sleeve 1. The inner end of the electrode cooperates with an inward projection or projections on the plug body 1 which are slightly spaced from said electrode to provide a gap across which a spark is adapted to jump while the outer end of said electrode extends through the aforementioned nut and is adapted for connection in any suitable manner with a conductor such as is indicated at 11, same being covered by insulation 10 and the outer end of the nut preferably being recessed as shown to receive said insulation.

A spark plug constructed in accordance with. my invention is advantageous for the reason that the tapered electrode 5 is capable of being forced with such tightness within the tapered opening of the sleeve 4 as to effectively prevent the escape of gas through said sleeve, and for the reason that the electrode 5 not only is readily removable whenever desired for cleaning or other purposes, but because of the outer body of the nut being of insulation, such removal may be effected without fear of receiving an electric shock even though current be passing through the electrode.

\Vhat I claim is 1. A spark plug comprising a hollow metallic body portion, a member secured'within said body portion and insulated therefrom, an electrode passing through said member,

and a nut threaded on said member and engaging said electrode to retain same Withinsaid member, said nut consisting of a metallio portion in threaded engagement ithsaid member and a portion of insulation surrounding said'metallic portion and serving to insulate the latter from the body portion of the plug.

2. A spark plug comprising a hollow metallic body portion, a member secured Within said body portion and insulated therefrom, said member having an inwardly tapering opening formed therein, an inwardly taperingelectrode engaged Within said openin anda nut threaded on said member and engaging said electrode whereby upon tight? I ening said rint the electrode is forced into into gas tight engagement with the Wall of said opening. 7 I

In witness hereof I have signed this specificati'ojn.

NQRMAN MACDONALD MARTIN. v 

